The present invention relates to spectrometers capable of measuring the interaction between atoms and molecules in the same species or interactions between atoms and molecules of different species.
Broadly, spectroscopy relates to the absorption of electromagnetic radiation (“light”) by molecular or atomic species. A wide variety of spectrometers are known. These include infrared (IR) spectrometers, which principally measure differences in molecular vibrational states, ultraviolet-visible (UV-VIS) spectrometers, which principally measure differences in molecular electronic states, and nuclear magnetic resonance (NMR) spectrometers, which principally measure differences in molecular nuclear spin states.
Typically, a sample of interest is exposed to a spectrum of light and the resulting light is compared to the spectrum of light absent the sample of interest. By subtracting the detected spectra with and without the sample of interest, an absorption spectrum is created. Such a one-dimensional spectrum typically has frequency as the independent variable and absorption as the dependent variable. The absorption peaks in the spectrum are indicative of vibrational/electronic/nuclear spin energy states in the species of interest.
There are thousands of known applications for spectroscopy. One application of spectroscopy is to identify or quantify molecular species based upon those species' characteristic IR/UV-VIS/NMR signatures. For example, spectroscopy is used to measure invisible gases in the atmosphere and the oxygenation of human blood. Another application is to use spectroscopy to gain information about a species' molecular vibrational/electronic/nuclear states, thus providing clues to the species' structure or properties. For example, spectroscopy is used to determine structural changes in chlorophyll upon exposure to sunlight. In still another application, spectroscopy is used to measure the interaction between atoms within a species or between atoms of two or more different species. For example, spectroscopy is used to measure the interaction between water molecules in ice.
Multidimensional spectroscopy, generally, correlates a one-dimensional spectrum to some other variable. The other variable might be time, phase of the light, or the presence of additional molecular excitations. Because the absorption spectrum evolves with time, etc., multidimensional spectroscopy can give unique clues to the structure or function of a species. Typically, multi-dimensional spectroscopy is limited to two or three additional variables because of the difficulty of visualizing and analyzing the resulting spectra. However, there is no theoretical limit to the number of dimensional variables that might be measured for a species in a given measurement.
Multidimensional NMR is the best developed form of multi-dimensional spectroscopy. Multidimensional NMR differs from one dimensional NMR in that more than one radio frequency pulse is applied to the sample, the additional pulses making possible the additional dimensional variables. Because of the ease of making radio pulse sequences, there are hundreds of different types of multidimensional NMR measurements that can be made. Multidimensional NMR has facilitated great progress in the fields of proteomics, helping scientists to understand the global structure of proteins in the solution phase. Multidimensional NMR has also provided insight into receptor binding and small molecule signaling by allowing scientists to measure distances between species once they have bound.
Multidimensional infrared, visible, and ultraviolet spectroscopy also holds great promise for the fields of proteomics, drug binding and small molecule signaling. In particular, multidimensional infrared spectroscopy can provide unique information about the structure of a protein and the protein's interaction with its environment. Ultraviolet-visible multidimensional spectroscopy can also provide unique information about the structure of a protein and the movement of charges about the protein. Additionally, in comparison to multidimensional NMR, multidimensional IR and UV-VIS spectroscopy offer better time resolution of dynamic structural changes, and smaller duty cycles for complex measurements.